| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive optical information recording/reproducing device improving recording density and hardly causing out-of-AT without using a special optical element. SOLUTION: A light beam outgoing from a semiconductor laser 21 becomes parallel light ray beams by a collimate lens 22 to be shaped to the beam with a prescribed intensity distribution by a beam shaping prism 23. Then, the beam is divided to three luminous flux by a diffraction grating 26, and further, the luminous flux S polarized by a polarizing beam splitter 27 are totally reflected to be converged on an optical card 1 by an objective lens 301 through a mirror 28. Three light beam spots converged on the optical card 1 are used for recording, reproducing, AF control and AT control respectively. The reflected light from light beam spots formed on the optical card 1 become the parallel luminous flux through the objective lens 301 again, and are reflected by the mirror 28, and are P polarized by the polarizing beam splitter 27, and further, are reflected by a reflection mirror 31 to be led to a photodetector 34. |
